The present invention relates to a magnetic bubble memory with unimplanted motifs.
It more particularly applies to the storage of binary information or bits, materialized in the form of isolated magnetic domains, called bubbles. These generally cylindrical domains have the reverse magnetization to that of the remainder of the magnetic material (garnet) constituting the layer in which these domains are formed. In this memory, the duplication of the magnetic bubbles makes it possible to carry out bit by bit duplication or bit block duplication.
In a monocrystalline magnetic layer, such as a magnetic garnet film, supported by an amagnetic monocrystalline garnet, the magnetic bubbles or domains are stable through the application of a continuous magnetic field Hp perpendicular to the plane of the magnetic layer. In practice, this magnetic layer is created by a permanent magnet, thus ensuring the non-volatility of the information contained in the memory.
In a magnetic bubble memory, the displacement of the bubbles is brought about by applying a rotary continuous field H.sub.T in a direction parallel to the surface of the magnetic layer. The bubbles are displaced around the so-called propagation motif defined in the upper part of the magnetic layer.
These motifs are in the form of disks, lozenges, triangles, T's, etc and can be produced from an iron and nickel-based material, or can be obtained by implanting ions in the upper part of the magnetic layer, across a mask making it possible to define the shape of these motifs. In view of the fact that ion implantation only takes place around the motifs, in the latter case, these motifs are called unimplanted or non-implanted motifs. The propagation motifs are generally contiguous. As a result of their shape, two adjacent motifs define two cavities or hollows between them.
The displacement of the bubbles along these motifs generally takes place for a time equal to one third of the rotation period of the planar magnetic field H.sub.T, the bubbles remaining stationary in the cavities defined between two adjacent motifs throughout the remainder of the cycle. In this way, shift registers are obtained in which the binary information 1 is represented by the presence of a bubble and the binary information "o" by the absence of a bubble.
In addition, to these propagation motifs, it is necessary to use electrical conductors for carrying out writing, information recording, non-destructive reading, register-to-register transfer and erasure functions in the bubble memory.
One of the main types of known magnetic bubble memories comprises a system of so-called minor loops or registers used for the storage of information, associated with one or two so-called major loops or registers forming the access stations to the memory. The minor loops are longitudinally juxtaposed and the major loops are oriented perpendicularly to the minor loops. The magnetic bubbles in the minor loops can be transferred into the major loops and vice versa, via unidirectional or bidirectional transfer gates.
When only a single major loop is used, information reading and writing takes place by means of this single loop. In the first case, reference is made to a memory having a major--minor organisation. Conversely, when use is made of two major loops, writing of the information takes place via one of these two loops and reading of the information via the other loop. These major loops are generally located on either side of minor loops. In the latter case of two loops, reference is generally made to a memory having a series--parallel organization.
In the aforementioned bubble memories, the production of a bubble on a major loop, corresponding to the writing of information, is brought about by applying a high current to a generally U-shaped conductor, traversing the propagation motifs constituting the major loops. This operation, generally known as nucleation, is performed when the bubble is in a cavity defined between two adjacent motifs.
Following nucleation, the bubble is then propagated, by the application of a rotary field H.sub.T, on the major loop towards the transfer gates, in order to transfer the bubble from the major loop to a minor loop. These transfer gates are generally formed by a U-shaped conductor traversing the motifs forming the minor loop. The application of a current pulse to this conductor makes it possible to extend each bubble between the tops of the propagation motifs and the major loop and those corresponding to the minor loop and then the stopping of the current pulse brings about the contraction of the bubbles on the minor loop. The transfer is then carried out, so that the information is stored on the minor loop.
The reading of this information takes place by transferring a magnetic bubble from a minor loop to a major loop. The transfer takes place in the manner described hereinbefore.
In order to read information in a non-destructive manner, the corresponding bubble must be duplicated. In the case of a bubble by bubble nucleation, said duplication is carried out by means of a conductor passing through the major loop, to which a current pulse is applied, leading to the elongation of the bubble on either side of the propagation paths, followed by the splitting of said bubble into two. One of these bubbles, transferred on a detection path, can be destructively detected by a magnetoresistive detector, generally based on iron and nickel, whilst the other bubble is reinjected into the minor loop at the location occupied by the original bubble.
A bubble memory operating on this principle has been described in U.S. Pat. No. 4,253,159, filed on Dec. 3, 1979 and entitled "ion-implanted bubble memory with replicate port". In this patent, use is made of a single major loop and unimplanted propagation motifs.
Magnetic bubble memories having as their propagation motifs, unimplanted motifs and having a structure and operation of the type described hereinbefore (cf the aforementioned U.S. Patent) only make it possible to carry out a duplication of the bubbles corresponding to a bit by bit duplication. These memories do not make it possible to carry out the duplication of a bit block or group.